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Flare Stack Design

molecular seal & water seal

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#1 Phenol

Phenol

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Posted 05 September 2016 - 02:54 AM

Members,

 

Two alternates - Molecular seal and Velocity seal are considered in flare stack design to avoid oxygen ingress into the stack.

 

What is the selection criteria among these seals.

 

Also whether Water Seal  at the bottom of the stack is a must in all cases ??

 

Rajan

 

 

 

 



#2 fallah

fallah

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Posted 05 September 2016 - 03:40 AM

Rajan,

 

Molecular seal:

 

- Not proper in cold environment because is capable to collect liquids following which there would be the risk of freezing and blockage

- Provide greater reduction in required purge gas

- Considerable large (higher structural and wind loads) and more expensive

 

Velocity seal:

 

- Proper in cold environment because doesn't collect liquid

- Provide lower reduction in required purge gas

- Smaller size and less expensive

 

Water seal at the stack bottom isn't a must and can be replaced by proper seal along with the required purge gas adjustment


Edited by fallah, 05 September 2016 - 03:44 AM.


#3 Bobby Strain

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Posted 05 September 2016 - 09:49 AM

Are you only using us for your project? Do you have any other resources? Do you have any books?

 

Bobby



#4 ankur2061

ankur2061

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Posted 05 September 2016 - 01:10 PM

Phenol,

 

Refer API STD 521 (Section 5.7.6 , Purging). Detailed explanation including merit and demerits of the molecular seal and velocity seal are provided. Calculations for purge gas flow rate for both types of seals are also provided in thi section

 

Section 5,7.8 gives a description of liquid (water or water-glycol mixture) seal drums and its applicability for flares.

 

Regards,

Ankur






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